Monorail vehicles, per se, are old in the art. For example, see U.S. Pat. Nos. 4,065,007 and 4,074,632. A vehicle having a vertically disposed rack is shown in FIG. 4 of U.S. Pat. No. 3,817,184. Horizontally disposed vehicles which ride on tracks about three feet above the floor are known. The provision of an actuator for controlling the vehicle drive wheel between drive and stop positions is per se old as per U.S. Pat. Nos. 3,818,837; 3,356,040; 3,903,810; 3,858,626.
The present invention is directed to solution of the problem of constructing such a driverless vehicle so as to be adapted for supporting vertically disposed work pieces along an assembly line with minimum height off the floor and minimun width transverse to the direction of movement.